strip devsupport from prod builds

Reviewed By: zen

Differential Revision: D2912192

fb-gh-sync-id: ff89fc16dcd86481657197055e31d2b67a94e7ea
shipit-source-id: ff89fc16dcd86481657197055e31d2b67a94e7ea

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManagerImpl.java

@@ -58,8 +58,7 @@ import com.facebook.react.common.ReactConstants;
 import com.facebook.react.common.annotations.VisibleForTesting;
 import com.facebook.react.devsupport.DevServerHelper;
 import com.facebook.react.devsupport.DevSupportManager;
-import com.facebook.react.devsupport.DevSupportManagerImpl;
-import com.facebook.react.devsupport.DisabledDevSupportManager;
+import com.facebook.react.devsupport.DevSupportManagerFactory;
 import com.facebook.react.devsupport.ReactInstanceDevCommandsHandler;
 import com.facebook.react.modules.core.DefaultHardwareBackBtnHandler;
 import com.facebook.react.modules.core.DeviceEventManagerModule;
@@ -275,15 +274,11 @@ import static com.facebook.react.bridge.ReactMarkerConstants.*;
     mJSMainModuleName = jsMainModuleName;
     mPackages = packages;
     mUseDeveloperSupport = useDeveloperSupport;
-    if (mUseDeveloperSupport) {
-      mDevSupportManager = new DevSupportManagerImpl(
-          applicationContext,
-          mDevInterface,
-          mJSMainModuleName,
-          useDeveloperSupport);
-    } else {
-      mDevSupportManager = new DisabledDevSupportManager();
-    }
+    mDevSupportManager = DevSupportManagerFactory.create(
+        applicationContext,
+        mDevInterface,
+        mJSMainModuleName,
+        useDeveloperSupport);
     mBridgeIdleDebugListener = bridgeIdleDebugListener;
     mLifecycleState = initialLifecycleState;
     mUIImplementationProvider = uiImplementationProvider;

ReactAndroid/src/main/java/com/facebook/react/devsupport/DevSupportManagerFactory.java

@@ -0,0 +1,62 @@
+package com.facebook.react.devsupport;
+
+import javax.annotation.Nullable;
+
+import java.lang.reflect.Constructor;
+
+import android.content.Context;
+import android.util.Log;
+
+import com.facebook.react.common.ReactConstants;
+import com.facebook.react.common.build.ReactBuildConfig;
+
+/**
+ * A simple factory that creates instances of {@link DevSupportManager} implementations. Uses
+ * reflection to create DevSupportManagerImpl if it exists. This allows ProGuard to strip that class
+ * and its dependencies in release builds. If the class isn't found,
+ * {@link DisabledDevSupportManager} is returned instead.
+ */
+public class DevSupportManagerFactory {
+
+  private static final String DEVSUPPORT_IMPL_PACKAGE = "com.facebook.react.devsupport";
+  private static final String DEVSUPPORT_IMPL_CLASS = "DevSupportManagerImpl";
+
+  public static DevSupportManager create(
+      Context applicationContext,
+      ReactInstanceDevCommandsHandler reactInstanceCommandsHandler,
+      @Nullable String packagerPathForJSBundleName,
+      boolean enableOnCreate) {
+    if (!enableOnCreate) {
+      return new DisabledDevSupportManager();
+    }
+    try {
+      // ProGuard is surprisingly smart in this case and will keep a class if it detects a call to
+      // Class.forName() with a static string. So instead we generate a quasi-dynamic string to
+      // confuse it.
+      String className =
+          new StringBuilder(DEVSUPPORT_IMPL_PACKAGE)
+              .append(".")
+              .append(DEVSUPPORT_IMPL_CLASS)
+              .toString();
+      Class<?> devSupportManagerClass =
+          Class.forName(className);
+      Constructor constructor =
+          devSupportManagerClass.getConstructor(
+              Context.class,
+              ReactInstanceDevCommandsHandler.class,
+              String.class,
+              boolean.class);
+      return (DevSupportManager) constructor.newInstance(
+          applicationContext,
+          reactInstanceCommandsHandler,
+          packagerPathForJSBundleName,
+          true);
+    } catch (Exception e) {
+      throw new RuntimeException(
+          "Requested enabled DevSupportManager, but DevSupportManagerImpl class was not found" +
+              " or could not be created",
+          e);
+    }
+  }
+
+}